The present invention relates to a sheet feeding device for feeding a sheet, having a sheet cassette mounted in a machine main unit such as a copying machine.
Conventionally, this type of sheet feeding device has provided a sheet cassette, for holding a plurality of sheets in a stacked state, attachably and detachably mounted on the machine main unit. For example, depending on a sheet size, such as B4 and A4, a plurality of sheet cassettes corresponding to each of sizes are provided. When necessary, the sheet feed cassette is replaced with the another one. On the other hand, in the machine main unit, a shaft which is extended in a width direction of the sheets stacked in the sheet cassette and a sheet feeding roller which is driven to be rotated by the shaft are disposed. By the sheet feeding roller, sheet is fed one by one from the sheet cassette to the machine main unit.
To securely separate cut-form sheet one-by-one and satisfactorily feed it, the sheet feeding roller should be contacted with the sheet to be fed with a predetermined positional relationship in the width direction and should be rotated. However, when the sheet size is changed, because the sheet feeding roller position against the sheet is changed, a trouble may occur in feeding the sheet. As the countermeasures, thus far, various technologies where the position of the sheet feeding roller is changed according to the sheet size have been proposed.
For example, in the above technology which has been disclosed in Japanese Patent Provisional Publication SHO 60-19627, a sheet cassette is mounted in a direction perpendicular to the sheet feeding direction along a shaft which pivotally supports a sheet feeding roller, the sheet feeding roller being moved by the motion thereof. In the technology which has been disclosed in Japanese Utility Model Provisional Publication SHO 62-150439, a triangle plate is mounted on a sheet feeding roller, the triangle plate being moved when the feed cassette is mounted, thereby leftwardly and rightwardly moving the sheet feeding roller.
However, in the former type sheet feeding device, since the sheet cassette should be mounted in the direction perpendicular to the sheet feeding direction, the shape of the entire machine is restricted, resulting in a problem in designing other sections of the machine. On the other hand, in the latter type of sheet feeding device, as the sheet size increases, the triangle plate is remarkably extended, resulting in a problem where the entire machine size increases.